How your neighbor can make you fat (or thin)

Deepak Chopra

Published
4:00 am PDT, Monday, September 21, 2009

A new field of sociology is studying "social contagion," a deeply mysterious phenomenon that could change everything we think about our behavior. We all experience how fads and trends work. Out of the blue, everybody seems to be doing something new, whether it's texting, fleeing My Space for Facebook, or playing a new video game. Fads are contagious behavior. You catch them from other people. Yet no one knows how behavior goes viral. What makes a group of people all decide to act the same way?

This becomes a crucial medical question if you want a group to stop doing something harmful — getting young people not to smoke, for example, or persuading a whole population to stop getting obese. The most advanced work on this question has come from two researchers at Harvard, Nicholas Christakis and James Fowler, whose new book, Connected, was previewed in a recent New York Times Sunday magazine article. Christakis and Fowler analyzed data from the nation's biggest heart study, which has followed three generations of citizens in Framingham, Mass. They looked into the behavior of over 5,000 people who were mapped into 51,000 social connections with family, friends, and co-workers.

Their first discovery was that when someone gains weight, starts smoking, or gets sick, close family members and friends are around 50% more likely to behave the same way. This reinforces a social-science principle that is decades old: behavior runs in groups. We have all experienced it as peer pressure, or by knowing families where everyone seems to be overweight or a smoker. The reverse is also true. If you run with a healthy crowd, you are more likely to adopt healthy behavior yourself. Not just health is involved; almost any behavior can be contagious. In a dorm at college, if you happen to room with someone with good study habits and high grades, your grades are likely to improve by association.

But the second finding from Christakis and Fowler was far more mysterious. They found that social connections can skip a link. If person A is obese and knows person B who isn't, a friend of person B is still 20% more likely to be obese, and a friend of that friend is 10% more likely. This "three degrees of connection" holds good for all kinds of behavior. A friend of a friend can make you prone to smoking, unhappiness, or loneliness. The statistics are there to prove it, even though you have never met this friend of a friend.

The findings of Christakis and Fowler suggest invisible connectors that run through a whole society. If their research holds up, think about the implications. The notion of a collective unconscious was posed almost a century ago by the Swiss psychologist C. G. Jung, who also claimed that we all have a shadow side that hides in the unconscious. Did Jung hit on invisible connectors long before data came along to support him? That's really a side question to the main one: What kind of connection can exist invisibly, without people talking to each other, watching how each other behaves, or even knowing about each other's existence?

While pondering this issue, I'd like to point out that the same questions apply to the brain. When your brain is engaged in a behavior, millions of neurons "catch" the same intention and behave in synch without visible connections. Different areas of the brain light up simultaneously. We don't see one neuron teaching another the new behavior, nor do we find a hidden telephone system that transmits the new intention — such as deciding to get out of your chair and grab a glass of orange juice — from a starting point in one part of the brain to other locations. Instead, every neuron gets on board at the same time to carry out your intention.

These are complex issues, and I'm giving only a hint of how mysterious they are. But the new research on social contagion is exciting, because it supports the notion that there is actually one mind that coordinates not just how people catch on to fads or decide to imitate each other, not just how distant brain cells know what other brain cells are doing, but far-flung phenomena like how a baby learns to speak and how twins separated by thousands of miles suddenly know what's happening to each other. These invisible connectors are showing up in many, many areas of life. Social contagion is making news because we all like to rely on data, but the possibility that we all participate in one mind challenges religion, philosophy, and the meaning of life itself.